Image forming device

ABSTRACT

A second passage  20  is arranged on a side opposite to a discharge port  16  relative to a first passage  18.  Additionally, an intercepting member  24  is provided which intercepts the communication between the first passage  18  and the insertion port  14  and allows the insertion port  64  to communicate only with the second passage  20,  at a portion of the first passage  18  near the insertion port  14,  whereby the intercepting member  24  intercepts the communication between the first passage and the insertion port  14  at a prescribed timing.

TECHNICAL FIELD

The present invention relates to an image formation apparatus such ascopying machines, printers, and plotters.

BACKGROUND TECHNIQUE

As the output apparatus of computers and work stations, there are knownink-jet type image formation apparatuses which form images by ejectingan ink onto a recording medium like a recording paper sheet, andelectrophotography type image formation apparatuses which forms imagesby use of a developing agent on a recording medium. Some of such imageformation apparatuses have an insertion port for inserting a recordingmedium and a discharge port for discharging the recording medium on thesame side, and have a passage for introducing the recording medium tothe insertion port on the same side as the ports. Some of the imageformation apparatuses have a detection sensor near the insertion portfor detecting the recording medium to measure the length of therecording medium in formation of the image on the recording medium.

Such an image formation apparatus having the aforementioned passage andthe detection sensor measures the length of the recording medium bydetecting with the sensor the front end of the recording medium insertedthrough the passage and the insertion port, delivering further therecording medium toward the discharge port, and detecting with thesensor the rear end of the recording medium. Thus the length of therecording medium is measured by detection of the front end and the rearend of the recording medium by the detection sensor. After the lengthmeasurement of the recording medium by detection of the front end andthe rear end, the recording medium is delivered back from the dischargeport toward the insertion port (in the direction reverse to the lengthmeasurement direction), thereby the recording medium is set in a standbystate for printing.

However, in the case where the discharge port is placed above theinsertion port and the recording medium is long, the recording mediummay hang down from the discharge port to come close to the passage atthe time when the length measurement is completed by detection of therear end of the recording medium delivered through the passage and theinsertion port. After the length measurement, the recording medium issent back in the direction reverse to the length measurement to be readyfor printing. In this state, the rear end portion of the recordingmedium may reach the passage. Thereby, the rear end of the recordingmedium may be brought into contact with the front end thereof, and maybe wound by the front end to introduce the rear end into the dischargeport to cause paper jamming undesirably. Such jamming can occur evenwith the insertion port placed above the discharge port, if the rear endportion of the recording medium hangs down.

Furthermore, some of the ink-jet type or the electrophotography type ofimage formation apparatuses have the insertion port for inserting therecording medium and the discharge port for discharging the recordingmedium on the same side, and additionally an insertion table on the sameside for introducing the recording medium into the insertion port.

For inserting the recording medium into the insertion port for delivery,the recording medium is laid on the insertion table, and is introducedtherefrom into the insertion port. A detection sensor is placed near theinsertion port to detect the recording medium. On detection of the frontend of the recording medium by this detection sensor, the deliveryroller starts to deliver the recording medium.

Some of the image formation apparatuses having the insertion table andthe detection sensor as mentioned above form the image on the recordingmedium after measurement of the sheet length of the recording medium. Insuch an image formation apparatus, the recording medium is introducedfrom the insertion table into the insertion port; the front end of therecording medium is detected by the sensor; the recording medium isdelivered toward the discharge port; and the rear end is detected by thesensor. In such a manner, the length of the recording medium is derivedby detection of the front end and the rear end. The recording mediumafter the length measurement is delivered back from the discharge porttoward the insertion port (in the direction reverse to the lengthmeasurement) to be set in a standby state for printing.

However, in the case where the discharge port is placed above theinsertion port and the recording medium sheet is long, the front endportion of the recording medium may possibly hang down from thedischarge port onto the insertion table and may be inserted again intothe insertion port to cause paper jamming. Such jamming is liable to becaused in image formation on a long sheet of the recording medium.

Such jamming can be prevented by providing a guide or a like member tolead the recording medium discharged from the discharge port to beisolated from the insertion port.

However, if the recording medium curls as a whole or the front endthereof is curled by moisture absorption or another cause, the recordingmedium, which is discharged from the discharge port to a positiondistant to the insertion port, can hang down onto the insertion tableagain and be drawn into the insertion port to cause jamming.

DISCLOSURE OF THE INVENTION

The present invention intends to provide an image formation apparatuswhich does not cause paper jamming, under the above situations.

A first embodiment of the image formation apparatus of the presentinvention for achieving the above object, has an insertion port forinserting a recording medium and a discharge port for discharging therecording medium provided on the same side, and a first passage forguiding the recording medium to the insertion port also on the same sideas above, wherein

(1) the apparatus has a second passage provided on a side opposite tothe discharge port relative to the first passage and communicating withthe insertion port.

(2) The first passage and the second passage preferably join togethernear the insertion port, and

(3) an intercepting member is preferably provided which intercepts thecommunication between the first passage and the insertion port at aprescribed timing to allow the insertion port to communicate only withthe second passage.

A second embodiment of the image formation apparatus of the presentinvention for achieving the above object has an insertion port forinsertion of a recording medium and a discharge port for discharging therecording medium provided on the same side, and an insertion table forguiding the recording medium to the insertion port also on the same sideas above, wherein

(4) the insertion table has a stair at the border between a portion nearto the insertion port and an adjacent portion distant from the insertionportion, and

(5) the apparatus has preferably a blocking member for blocking thespace communicating with the insertion port at a prescribed timing at oraround the stair.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates schematically an ink-jet type image formationapparatus of a first embodiment in a state that the front end of arecording medium is placed in a first passage.

FIG. 2 illustrates schematically the ink-jet type image formationapparatus in a state that the rear end of the recording medium isdetected by a detection sensor.

FIG. 3 illustrates schematically the ink-jet type image formationapparatus in a state that the recording medium is guided into a secondpassage.

FIG. 4 is a flow chart showing the steps of forming an image on arecording medium by the ink-jet type image formation apparatusillustrated in FIG. 1.

FIG. 5illustrates schematically an intercepting member.

FIG. 6 illustrates schematically an ink-jet type image formationapparatus of a second embodiment of the present invention in a statethat the front end of a recording medium is placed in a first passage.

FIG. 7 illustrates schematically the ink-jet type image formationapparatus shown in FIG. 6 in a state that the rear end of the recordingmedium is detected.

FIG. 8 illustrates schematically the ink-jet type image formationapparatus shown in FIG. 6 in a state that the recording medium is guidedto a second passage.

FIG. 9 illustrates schematically an ink-jet type image formationapparatus of a third embodiment of the present invention in a state thatthe front end of a recording medium is placed on an insertion table at aportion thereof distant from the insertion port.

FIG. 10 illustrates schematically a state of a recording medium justbefore the front end thereof reaches a detection sensor at a dischargeport.

FIG. 11 illustrates schematically a state of a recording medium hangingdown from the discharge port.

FIG. 12 illustrates schematically a state that the front end of arecording medium brought onto the insertion table is blocked by ablocking member.

FIG. 13 illustrates schematically the blocking member.

FIG. 14 illustrates enlargedly the state of a portion of the spacearound a stair where the space communicating with the insertion port isblocked by the blocking member.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is explained by reference to drawings, taking asan example an ink-jet type image formation apparatus.

FIGS. 1-3 illustrate schematically constitution of an ink-jet type imageformation apparatus of a first embodiment of the present invention. FIG.1 illustrates a state of the front end of a recording medium placed in afirst passage. FIG. 2 illustrates a state of the rear end of therecording medium detected by a detection sensor. FIG. 3 illustrates thestate of the recording medium guided into a second passage.

In ink-jet type image formation apparatus 10, insertion port 14 forinserting recording medium (paper) 12, and discharge port 16 fordischarging recording medium 12 are provided on the same side. Firstpassage 18 for introducing recording medium 12 to insertion port 14 isprovided on the same side as insertion port 14. Second passage 20 isprovided on the side opposite to discharge port 16 relative to firstpassage 18, and this second passage 20 communicates with insertion port14. These first and second passages 18,20 are joined together in thevicinity of insertion port 14. In a portion of insertion port 14 nearthe joining part, detection sensor (photointerrupter) 22 is provided formeasuring the length of recording medium 12 for image formation thereon.The length of recording medium is measured by detecting the front endand the rear end of recording medium 12 and treating the detectionsignals by a computing element (not shown in the drawings).

In a portion of first passage 18 near to insertion port 14, interceptingmember 24 is provided which intercepts the communication between firstpassage 18 and insertion port 14 and allows communication of insertionport 14 with second passage 20 only. This intercepting member 24intercepts the communication between first passage 18 and insertion port14 at the timing shown later. Another detection sensor(photointerrupter) 23 is provided between paper discharging roller 34and discharge port 16. Printing head 40 is provided between deliveryroller 32 and paper discharge roller 34. The printing head 40 forms animage by ejection of ink by reciprocation movement in a directionperpendicular to the drawing paper sheet of FIG. 3.

The steps of formation of an image on recording medium 12 with theink-jet type image formation apparatus illustrated in FIG. 1 isexplained by reference to FIG. 4.

In printing with ink-jet type image formation apparatus 10, the lengthof recording medium 12 is measured prior to formation of an image onrecording medium 12. The measurement of the length of recording medium12 is conducted as follows. Recording medium 12 is placed on firstpassage 18 and is inserted in the arrow-A direction into insertion port14 as shown in FIG. 1 to allow recording medium 12 to push detectionsensor 22. By the pushing action against the detection sensor 22 byrecording medium 12, sensor portion 22 a of detection sensor 22 istilted, thereby detecting the front end of recording medium 12 (S1), andstarting driving roller 26 to rotate in the normal direction (normalrotation) (S2). By this rotation, recording medium 12 held betweendriving roller 26 and delivery roller 28 is delivered by driving roller26 and guide plate 30. Recording medium 12 is further held and deliveredby a pair of rollers 34 to discharge port 16. In such a manner,recording medium 12 is held between driving roller 26 and deliveryrollers 28,32, and between discharge rollers 34, and comes to be sentout through discharge port 16. At the time when the front end portion 12a is discharged from discharge port 16 and hangs down, and the rear endof recording medium 12 has passed detection sensor 22 a shown in FIG. 2,tilted sensor portion 22 a restores to the original state to detect therear end of recording medium 12 (S3). On detection of the front and therear end of recording medium 12, the detection signals are treated bycomputing element (not shown in the drawings) to derive the length ofrecording medium 12, and driving roller 26 is stopped once (34).

At the time when driving motor 26 has once stopped (an example of the“prescribed timing” in the present invention), motor 24 b (see FIG. 5)is rotated by a prescribed extent (S5) to raise interception plate 24 aof intercepting member 24 to intercept the communication between firstpassage 18 and insertion port 14 as shown in FIG. 3. Thereby, insertionport 14 communicates only with second passage 20. Thereafter, drivingroller 26 is rotated in the arrow-C direction (reverse rotation) (S6).By this rotation, recording medium 12 having been delivered by drivingroller 26 and delivery rollers 28,32 is guided to second passage. Whenthe front end of recording medium 12 has been detected by detectionsensor 23 (S7), driving roller is stopped once, and recording medium 12is in a state of standby for printing (S8).

For returning recording medium 12 to the standby state for the printingby the reverse rotation of driving roller 26, intercepting plate 24 a ofintercepting member 24 intercepts the communication between firstpassage 18 and insertion 14 to communicate insertion port 14 with secondpassage 20 only, so that recording medium 12 is guided to the secondpassage. When recording medium 12 begins to be guided to the secondpassage, front end portion 12 a of recording medium 12 is still hangingdown from discharge port 16 to be close to first passage 18. However,since recording medium 12 is guided to the second passage, the rear endportion of recording medium 12 cannot be caught and wound by front endportion 12 a of recording medium 12. Thereby, recording medium 12 doesnot enter discharge port 16, which prevents paper jamming.

When recording medium 12 has returned to the standby state and drivingroller 26 has stopped once (S8), driving roller 26 is started to rotatein the normal direction (S9). During the printing, detection sensor isdetecting continuously recording medium 12 (S10). When the rear end ofrecording medium 12 has been passed detection sensor 23 after completionof the printing, detection sensor 23 comes to be turned off (S11), anddriving roller 26 is stopped according to the signal showing theturning-off of detection sensor 23 (S12). Thereafter, motor 24 b (seeFIG. 5) is turned by a prescribed extent to lower interception plate 24a of intercepting member (S13). Thereby, first passage 18 is allowed tocommunicate with insertion port 14 for insertion of recording medium 12from first passage 18.

Intercepting member 24 is explained by reference to FIG. 5.

FIG. 5 illustrates schematically an intercepting member.

Intercepting member 24 comprises motor 24 b, and a gear 24 c fixed tothe rotation axis of this motor 24 b. Gear 24 c engages with gear 24 d.Interception plate 24 a is fixed to pivot of gear 24 d, and interceptionplate 24 a is turned by rotation of motor 24 b in the directions ofarrows D and D′. While recording medium 12 on first passage 18 (seeFIG. 1) is inserted into insertion port 14, interception plate 24 a isplaced at the position shown in FIG. 5 to communicate first passage 18with insertion port 14. On detection of the rear end of recording medium12 by detection sensor 22, motor 24 b rotates to turn interception plate24 a in the arrow D direction to intercept the communication betweenfirst passage 18 and insertion port 14.

In this example, intercepting member 24 is constituted of motor 24 b,gears 24 c,24 d, and other parts. However, intercepting member 24 may beconstituted of interception plate 24 a and a spring. In thisconstitution, interception plate 24 a is slightly energized by thespring in the arrow-D direction. With such slight energization ofinterception plate 24 a in the arrow-D direction, recording medium 12which has been inserted into insertion port 14 through first passage 18can pass through by pushing interception plate 24 a. When the rear endof recording medium 12 has passed interception plate 24 a, thecommunication between first passage 18 and insertion port 14 isintercepted owing to the energization of interception plate 14 a in thearrow-D direction by the spring. Otherwise, interception member 24 maybe constituted to serve also as detection sensor 22.

A second embodiment of the image formation apparatus of the presentinvention is explained below by reference to FIGS. 6-8.

FIG. 6 illustrates schematically an ink-jet type image formationapparatus of a second embodiment of the present invention in a statethat the front end of a recording medium is placed in a first passage.FIG. 7 illustrates schematically the ink-jet type image formationapparatus shown in FIG. 6 in a state that the rear end of the recordingmedium is being detected. FIG. 8 illustrates schematically the ink-jettype image formation apparatus shown in FIG. 6 in a state that therecording medium is guided to a second passage. In these drawings, thesame symbols and numerals are used for the corresponding constitutionalelements as in FIG. 1.

The ink-jet type image formation apparatus 50 is characterized in thatsecond passage 52 communicating with insertion port 14 is arranged so asto extend downward from the vicinity of driving roller 26. Secondpassage 52 is directed nearly perpendicularly to first passage 18, andinsertion port 14 is communicated selectively to one of first passage 18and second passage 18 by intercepting member 24.

The procedure of measuring the length of recording medium 12 and formingan image on recording medium 12 is similar to that described byreference to FIGS. 1-4. For returning recording medium 12 back to thestandby state by reverse rotation of driving roller 26, interceptionplate 24 a of intercepting member 24 intercepts the communicationbetween first passage 18 and insertion port 14, and allows communicationonly between second passage 52 and insertion port 14, whereby recordingmedium 12 is guided to the second passage. This prevents winding of rearend portion 12 b of recording medium 12 by front end portion 12 athereof to enter discharge port 16, and prevent paper jamming.

A third embodiment of the image formation apparatus of the presentinvention is explained below by reference to FIGS. 9-12.

FIGS. 9-12 illustrate schematically constitution of an ink-jet typeimage formation apparatus of a third embodiment of the presentinvention. FIG. 9 illustrates a state that the front end of a recordingmedium is placed on an insertion table at a portion thereof distant froman insertion port. FIG. 10 illustrates a state of a recording mediumjust before the front end thereof reaches a detection sensor at adischarge port. FIG. 11 illustrates a state of a recording mediumhanging down from the discharge port. FIG. 12 illustrates schematicallya state that the front end of a recording medium brought onto theinsertion table is blocked by a blocking member.

The ink-jet type image formation apparatus 60 has insertion port 64 forinsertion of recording medium 12 and discharge port 66 for dischargingrecording medium 12 provided on the same side, and additionallyinsertion table 68 for introducing recording medium 12 into insertionport 64 on the same side as discharge port 66 for discharging recordingmedium 12. Insertion table 68 has two portions: a portion 68 a near toinsertion port 64 and another portion 68 b distant from insertion port64, the nearby portion 68 a being lower by about 5 mm than the distantportion 68 b. Therefore, stair (level difference) 68 c is formed at theborder between nearby portion 68 a and distant portion 68 b. Above stair68 c, there is provided blocking member 74 which blocks the spacecommunicating with insertion port 64 in the vicinity of stair 68 c at aprescribed timing. This blocking member 74 is described later byreference to FIGS. 13-14.

Detection sensor (photointerrupter) 72 is provided in the vicinity toinsertion port 64 for detection of recording medium 12. The front endsand the rear ends of a sheet of recording medium 12 is detected by thisdetection sensor 72. The length of recording medium 12 is derived bytreating the detection signals with a computing element (not shown inthe drawing).

Another detection sensor (photointerrupter) 73 is provided for detectionof recording medium 12 between discharge roller and discharge port 66.In the region between delivery roller 32 and discharge roller 34,printing head 40 is provided which ejects ink with reciprocatingmovement in a direction perpendicular to the drawing paper sheet of FIG.9 to form an image. Driving roller 26 is constructed so as to rotate inthe directions shown by arrows B and C.

The process is explained for forming an image on recording medium 12 byink-jet type image formation apparatus 60 by reference to FIGS. 9-12.

For image formation with ink-jet type image formation apparatus 60,recording medium 12 is placed on distant portion 68 b of insertion table68, and is inserted in the arrow-A direction into insertion port 64 topush detection sensor 72. By pushing recording medium 12 to detectionsensor 72, sensor portion 72 a of detection sensor 72 is tilted todetect the front end of recording medium 12 and to start rotation ofdriving roller 26 in the arrow-B direction (normal rotation) Thereby,recording medium 12 is held between driving roller 26 and deliveryroller 28, and is delivered through the interspace between drivingroller 26 and guide plate 30.

For further delivery, recording medium 12 is held and delivered by apair of discharge rollers 34 toward discharge port as shown in FIG. 10.For further delivery of recording medium 12, front end portion 12 a ofrecording medium 12 is detected by detection sensor 73. At the timing ofdetection of the front end portion 12 a of recording medium 12 bydetection sensor 73 (“prescribed timing” in the present invention),blocking member 74 blocks communication of the space around stair 68 cwith insertion port 64. This blocking is described later by reference toFIGS. 13-14.

As described above, recording medium 12 is held and delivered by drivingroller 26, delivery rollers 28,32, and discharge rollers 34, and comesto be discharged through discharge port 66. Here, if front end portion12 a of recording medium 12 is curled by humidity absorption or othercauses, front end portion 12 a is brought onto insertion table 68 and isintroduced to insertion port 64 again following the insertion ofrecording medium 12.

At this time, however, as described above, the space communicating withinsertion port 64 is blocked in the space around stair 68 c by blockingmember 74. Therefore, front end portion 12 a of recording medium 12 isblocked by blocking member 74 so as not to be inserted into insertionport 64 as shown in FIG. 12. Thus, front portion 12 a of recordingmedium 12 discharged from discharge port 66 is prevented from secondentry into insertion port 64, not causing jamming.

Blocking member 74 is explained below by reference to FIGS. 13-14.

FIG. 13 illustrates schematically blocking member 74. FIG. 14illustrates enlargedly the state of a portion of the space around astair 68 c where the space communicating with insertion port 64 isblocked by the blocking member 74.

Blocking member 74 comprises motor 74 a, and a gear 74 b fixed to therotation axis of this motor 74 a. Gear 74 b engages with gear 74 c.Blocking plate 74 d is fixed to the pivot of gear 74 c, and blockingplate 74 d is turned by rotation of motor 74 a in the directions ofarrows D and D′. At the tip of blocking plate 74 d, delivery roller 74 eis fixed rotatably.

After insertion of recording medium 12 from insertion table 68 (see FIG.9), before detection of recording medium 12 by detection sensor 73,blocking plate 74 d is placed at the position shown in FIG. 9 or FIG.10, and the space communicating with insertion port 64 around stair 68 cis not blocked. At the timing when front end portion 12 a of recordingmedium 12 is detected by detection sensor 73, motor 74 a starts torotate to turn blocking plate 74 d in the arrow-D direction. Thereby,delivery roller 74 e comes to be fitted to stair 68 c with a pressingforce to allow the passing recording medium 12 only to pass therethroughand to block the space around stair 68 c communicating with insertionport 64. Thus, even if front end portion 12 a of recording medium 12having discharged from discharge port 66 is curled, reentry of front endportion 12 a thereof into insertion port 64 is prevented, wherebyjamming is prevented.

The recording medium 12 passing through stair 68 c is allowed to passalong stair 68 c without inconvenience in delivery of recording medium12. In this example, the level of portion 68 a of insertion table 68near insertion port 64 is made lower by about 5 mm than the level ofportion 68 b distant therefrom, whereas nearby portion 68 a may be madehigher by about 5 mm than distant portion 68 b.

Industrial Usefulness

As described above, the image formation apparatus of the firstembodiment of the present invention has a second passage provided on theside opposite to the discharge port relative to the first passage. Thissecond passage communicates with an insertion port. Therefore, therecording medium discharged through insertion port is delivered to thesecond passage, whereby the recording medium discharged throughinsertion port is prevented from contact with the recording mediumdischarged through discharge port. As the result, jamming caused bywinding of a part of the recording medium into discharge port isprevented.

The first passage and the second passage join together in the vicinityof the insertion port. The intercepting member, which interceptscommunication between the first passage and insertion port tocommunicate the insertion port only with the second passage, preventsmore surely the jamming caused by winding of a part of the recordingmedium into the discharge port.

The image formation apparatus of the second embodiment of the presentinvention has a blocking member for blocking, at a prescribed timing,the space which communicates with the insertion port. Therefore, even ifthe front end portion of the recording medium discharged from thedischarge port is curled, the recording medium does not reenter theinsertion port, whereby the jamming is prevented. Further, the recordingmedium passing through the stair is allowed to pass along the stairwithout inconvenience in delivery of the recording medium.

What is claimed is:
 1. An image formation apparatus having an insertionport for inserting a recording medium, a driving roller and a dischargeport for discharging the recording medium provided on one side of thedriving roller to turn back the recording medium, and a first passagefor guiding the recording medium to the insertion port also on the sameside of the driving roller as the insertion port and the discharge port,wherein the apparatus has, on the side opposite to the discharge portrelative to the first passage, a second passage which communicates withthe insertion port and guides only the recording medium delivered backafter passing through the first passage.
 2. The image formationapparatus according to claim 1, wherein the first passage and the secondpassage join together near the insertion port, and an interceptingmember is provided which intercepts the communication between the firstpassage and the insertion port at a prescribed timing to allow theinsertion port to communicate with the second passage only.
 3. An imageformation apparatus having an insertion port for inserting a recordingmedium, a driving roller and a discharge port for discharging therecording medium provided on one side of the driving roller to turn backthe recording medium, and a first passage for guiding the recordingmedium to the insertion port also on the same side of the driving rolleras the insertion port and the discharge port, wherein the apparatus hasa second passage which communicates with the insertion port and extendsin a direction nearly perpendicular to the first passage, and guidesonly the recording medium delivered back after passing through the firstpassage, and wherein said second passage is on an opposite side of thefirst passage relative to the discharge port.
 4. The image formationapparatus according to claim 3, wherein the first passage and the secondpassage join together near the insertion port, and an interceptingmember is provided which intercepts the communication between the firstpassage and the insertion port at a prescribed timing to allow theinsertion port to communicate with the second passage only.
 5. An imageformation apparatus having an insertion port for inserting a recordingmedium, a driving roller and a discharge port for discharging therecording medium provided on one side of the driving roller to turn backthe recording medium, and an insertion table for guiding the recordingmedium to the insertion port also on the same side of the driving rolleras the insertion port and the discharge port, wherein the insertiontable has a stair, near the insertion port and a blocking member isprovided which presses the recording medium being delivered and blocks aspace communicating with the insertion port at a prescribed timing at oraround the stair.